Many electronic devices include a removable accessory or component. A removable component is, for example, a battery in a mobile or portable device, like a mobile phone, a personal digital assistant, a mobile computer, a photo camera or a video camera; or an ink or toner cartridge in a printer or copier. To provide a proper function of the electronic device, it is necessary to detect whether a component is connected thereto, and if several components, like batteries, can be connected to the electronic device, how many components are connected thereto.
Some types of components have a communication interface which allows a communication or information transfer between the component and the electronic device. Such information may include authentication information which allows the electronic device to verify that the component is suitable and authorized to be used with the electronic device; operation parameters of the component, like the temperature (measured by a temperature sensor), or the charging state of a battery or the filling level of an ink or toner cartridge.
Some electronic devices are very small, so that space is an issue, and thus it is desirable to use only one port or terminal of the electronic device to provide both presence detection and communication, for cost reasons and for space reasons.